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> The plane flatly is uncertifiable without it. No amount of training would change this, as inverted stick forces are a failure of fundamental airworthiness req

> The plane flatly is uncertifiable without it. No amount of training would change this, as inverted stick forces are a failure of fundamental airworthiness requirements. I didn't know that. In that case though, would it even be allowed to disable MCAS as part of any SOP? As far as I recall the documentation did mention one obscure process indicating to the pilot to disable MCAS when it acted up like it did during the accidents. But I can't imagine it would be allowed to even have this as an operating procedure this when it puts the plane in a situation where it can't be certified? The whole thing is such a mess... It's clear they should have just redesigned the whole airframe to modern standards IMO.

salawat 4y ago
>But I can't imagine it would be allowed to even have this as an operating procedure this when it puts the plane in a situation where it can't be certified? Anything can be allowed with enough omission, lawyers, scapegoating, campaign donations, and enough tolerance for blood on one's hands. It's called regulatory capture and it's the fundamental conflict-of-interest between most engineering orgs and their in house Quality programs, with the exacerbating effect that if you can coerce the external regulatory forces to give you a pass, there's really nothing your Quality people can do but resign in a gesture of "I won't build that". You will never see the regulatory apparatus work as designed if it isn't willing to just say "No" to that which clearly violates prescriptive certification criteria.
tzs 4y ago
As was mentioned earlier, MCAS exists to modify the stick forces in certain circumstances. Those circumstances never occur in anything near normal flight. And if they do occur it is not like the stick force deviation from what regulations allows makes the plane not flyable. I've seen it described by pilots who have tested it as it makes it have a slightly softer feel for stall recovery. When the European Union Aviation Safety Agency was testing it for return to service they did full flights tests with and without MCAS and found that it was fine both ways [1]. So if something goes wrong with MCAS during a flight making it interfere with normal operation of the aircraft, then disabling it is quite reasonable. The odds that you will end up later in a situation where MCAS actually has to do something are extremely low, and the odds are even lower that the pilots won't be be able to handle it without the help from MCAS. And that's assuming you are in a stage of flight where it would even be used. MCAS is only active when flaps are up and the autopilot is disengaged, so most of the time for most flights it is out of the picture. MCAS seems to be one of those things that needs to have great care taken in its implementation because the danger from it mistakenly activating when it should not seems to be orders of magnitude higher than amount of safety benefit it provides when it correctly activates. They did not take that great care. [1] https://theaircurrent.com/aircraft-development/mcas-may-not-have-been-needed-on-the-737-max-at-all/ https://theaircurrent.com/aircraft-development/mcas-may-not-...
sokoloff 4y ago
The response to a pitch trim runaway (MCAS or otherwise) is anything but an obscure process to anyone sitting forward of the cockpit door on a 737. It’s a memory-item checklist, demonstrated in initial and recurrent training. (The pitch trim wheels are prominent in the cockpit and make a clanging noise while running as well.)

salawat 4y ago

>But I can't imagine it would be allowed to even have this as an operating procedure this when it puts the plane in a situation where it can't be certified? Anything can be allowed with enough omission, lawyers, scapegoating, campaign donations, and enough tolerance for blood on one's hands. It's called regulatory capture and it's the fundamental conflict-of-interest between most engineering orgs and their in house Quality programs, with the exacerbating effect that if you can coerce the external regulatory forces to give you a pass, there's really nothing your Quality people can do but resign in a gesture of "I won't build that". You will never see the regulatory apparatus work as designed if it isn't willing to just say "No" to that which clearly violates prescriptive certification criteria.

tzs 4y ago

As was mentioned earlier, MCAS exists to modify the stick forces in certain circumstances. Those circumstances never occur in anything near normal flight. And if they do occur it is not like the stick force deviation from what regulations allows makes the plane not flyable. I've seen it described by pilots who have tested it as it makes it have a slightly softer feel for stall recovery. When the European Union Aviation Safety Agency was testing it for return to service they did full flights tests with and without MCAS and found that it was fine both ways [1]. So if something goes wrong with MCAS during a flight making it interfere with normal operation of the aircraft, then disabling it is quite reasonable. The odds that you will end up later in a situation where MCAS actually has to do something are extremely low, and the odds are even lower that the pilots won't be be able to handle it without the help from MCAS. And that's assuming you are in a stage of flight where it would even be used. MCAS is only active when flaps are up and the autopilot is disengaged, so most of the time for most flights it is out of the picture. MCAS seems to be one of those things that needs to have great care taken in its implementation because the danger from it mistakenly activating when it should not seems to be orders of magnitude higher than amount of safety benefit it provides when it correctly activates. They did not take that great care. [1] https://theaircurrent.com/aircraft-development/mcas-may-not-have-been-needed-on-the-737-max-at-all/ https://theaircurrent.com/aircraft-development/mcas-may-not-...

sokoloff 4y ago

The response to a pitch trim runaway (MCAS or otherwise) is anything but an obscure process to anyone sitting forward of the cockpit door on a 737. It’s a memory-item checklist, demonstrated in initial and recurrent training. (The pitch trim wheels are prominent in the cockpit and make a clanging noise while running as well.)